Catalytic fuel igniters



M y 22, 1956 w. J. KUCZYNSKI ET AL CATALYTIC FUEL IGNITERS Filed Nov.22, 1950 IN VEN TOR.

WALTER J. KUCZYNSKI GEORGE J. LEHMANN United States Patent CATALYTICFUEL IGNITERS Walter J. Kuezynski, Newark, and George J. Lehmann,Arlington, N. J., assignors to Baker & Co., Inc., Newark, N. J., acorporation of New Jersey Application November 22, 1950, Serial No.197,164

11 Claims. (Cl. 317-83) This invention relates to catalytic igniters forgas burners, and is concerned in particular with maintaining suchigniters in a highly active state.

During the past few years hot wire igniters have been used more and moreto replace the common pilot flames in the ignition systems for domesticgas stoves and furnaces and for many industrial applications. Of theknown hot wire igniters there are those that require resistance heatingby a relatively high electric current before they may reach atemperature high enough to ignite a gaseous or atomized fuel. If suchigniters, when installed for operation, are maintained at all times atfuel ignition temperatures, which should be done to insure ignitionunder all conditions, such as when a burner flame becomes extinguishedthough the fuel continues to flow, then it is found that theydeteriorate rapidly, whereby ther useful life is substantially reduced,requiring replacement and involving expense and inconvenience.

More recently catalytic fuel igniters especially those embodying aheterophase arrangement have been employed in gas burner ignitionsystems. Such heterophase type igniters need not be maintained at atemperature high enough to combust a fuel, but may be kept at a muchlower temperature and still function properly. Besides having aheterophase configuration, igniters of this type are preferably formedof metals of the platinum group of alloys thereof or sinteredagglomerates of such metals or metal compositions.

Some fuels are, of course, more easily ignited than are others. Inparticular, manufactured gas, i. e. city gas, for example, will ignitemore readily than will natural gas.

It has now been found that when catalytic igniters are maintained in aheated condition below a certain temperature, more fully explainedhereinafter, they become less active and may, in some cases even withina few hours of disuse, lose their ignition efiiciency or even becomeunable to ignite catalytically some of the more diflicultly ignitablefuels. This loss in activity with respect to the more difficultlyignitable fuels is gradual and is dependent on several factors amongwhich are the temperature to which the igniter is heated, the nature ofthe flame to be produced, i. e. aerated or non-aerated, and the velocityat which the gas impinges on the igniter filament.

it is accordingly, an object of the invention to provide for maintaininga catalytic igniter in an active state with respect to fuels which areparticularly difficult to ignite. More specifically, it is an object ofthe invention to provide means and method for maintaining a catalyticigniter in an active state when employed in a flash-back system for gasburners, and yet not cause it to deteriorate and impair its usefulnessover long periods of operation. Further objects and various advantagesof the invention will become apparent from the following detaileddescription thereof, and from the accompanying drawing, the singlefigure of which is a wiring diagram showing an electric circuit for anigniter filament, and constructed according to the invention.

The present invention deals with the ignition of combustible gases bymeans of a catalytic igniter coil which is energized by a two stageapplication of electrical energy, whereby the first stage comprises thepassing of electrical energy through said coil at a value sufficient toheat the coil to a stand-by temperature below the ignition temperatureof the gas. The second stage comprises the momentary elevation of saidfirst stage energy at spaced intervals to occasionally or periodicallyraise the temperature of the igniter coil above the stand-bytemperature, thereby periodically reactivating the igniter coil tomaintain it in a stimulated and catalytically active state.

This repetitive periodically spaced flash activation is applied duringprolonged stand-by periods during which otherwise there occurs alowering of ignition efliciency or other deactivation of the catalyticigniter coil.

In order to overcome the decrease in the ignition efiiciency the ignitercoil is, in accordance with the invention subjected at spaced intervalsof time to an instantaneous flash of high heat i. e. a temporary heatingto a higher temperature than the stand-by temperature. This periodicallyspaced flash-heating i. e. higher heating stimulates or rejuvenates thecatalytic activity of the coil. The duration of this flashing (i. e.heating) operation may be of the order of a second or less. Longerflashing or heating is not necessary and may be detrimental to theigniter filament, especially where very fine filaments are involved.Where thicker filaments are used the high heating may last even longerthan one second. The exact temperature required for reactivation is notaccurately known, but as a general rule, it is essential that a regularoperating temperature be maintained below the ignition point of the gasand that the stand-by temperature be increased at appropriate intervals;which may be accomplished by energizing the circuit into which theigniter is inserted or the filament may be energized for a second or sowith a voltage of about 50% to 60% higher than the normal operatingvoltage. Under normal conditions of heat loss, since voltage is directlyproportional to power input and since the current remains approximatelythe same, then by energizing the filament with about a 50% increase involtage an approximate increase in temperature of about 50% is obtained.It necessarily follows therefore that any external means may be used toraise the temperature about 50% higher than normal operatingtemperatures in order to perform the method step of reactivating theigniter coil, and although the following description refers tointermittent heating by electrical means, which would appear to be themost obvious means, the method of my invention is not necessarilylimited to the use of such means, but rather such structure is in thenature of a preferred embodiment. The time interval between the heatflashes or intermittent catalyst rejuvenating heating may be of theorder of six hours or more.

In the case of natural gas and for coils formed of a platinum metal orof platinum metal alloys, the tem perature threshold above whichcatalytic activity remains unaltered is about 800 C. Such coils losetheir relative activity upon standing at temperatures below about 800 0;however, when formed to a heterophase configuration, they could functionadvantageously in the usual flash-back systems, at low temperatures, e.g. about 700 C. and even less, if their catalytic activity is notreduced upon standing. It is desirable, of course, to keep the standbytemperature for the coil as low as possible, since deterioration of thecoil occurs at high temperatures but is practically negligible at lowtemperatures of the order of 700 C. and less.

Since, an igniter is kept idle at standby temperature for frequentindefinite periods of time, it is good practice to provide an automatictime switch device in connection with the intermittent heating means forsupplying flashes of heat to the igniter coil at regular intervals, i.e., for example, every 6, 12 or 24 hours, depending upon thecharacteristics of the ignition system and other factors that influencethe speed of ignition in a given installation.

teferring now to the drawing showing a preferred apparatus forperforming the standby operation, there is shown a catalytic fueligniter filament l, in the form of a coiled coil, connected into anelectric circuit for maintaining the coil at a low standby temperatureand for automatically and periodically subjecting the coil to aninstantaneous heat flash. The coiled coil configuration of the filamentit is a preferred embodiment of the heterophase principle mentionedherein above.

The source of current, indicated by the reference numeral 2, may be thatthe ordinary electric circuit found in homes and in industrial plants.From this conventional electric supply, current is carried by theconductors 3 and 4 to the primary coil 5 of a transformer 6. Thesecondary coil 7 of the transformer 6 is connected at one end to thewire 8 which in turn is connccted to one end of the filament l. Theother ends of the secondary coil and the filament are joined to thewires 9 and 14) respectively, which close the circuit of the secondaryside of the transformer by being joined through an automatic time switchmechanism 11. A lead-off conductor 12 from between the ends of thesecondary coil 7 is also connected to the switch mechanism ill, thepoint of contact of the conductor 12 with the coil 7 being spaced fromthat end of the coil which is joined to the wire 3, by a distance ofabout two thirds the length of the coil.

The specific construction or" the automatic time switch 11 is well knownin the art and does not, per se, constitute part of the invention.Accordingly, a detailed description thereof is not necessary for thepurpose of this specification. it is sutficient state that the mechanism11 contains a switch 13 which is operable between the contacts 14 andfor alternately closing the circuit having tr e lead-off conductor 12and the circuit having wire 9. The mechanism 11 may be energized throughthe conductors 16.

Under standby conditions the switch is closed against the contact 14-whercby an electrical potential of e. g., about two volts may beimpressed across the filament i from the transformer 6. After apredetermined time interval, depending on the setting of the timingmechanism ii, the switch .13 will be flipped to the contact 15 and thenbacl; to the contact 14. When this occurs the filament 1 becomesmomentarily connected into a circuit having a potential of, for example,about three volts, whereby the filament will be heated substantiallyabove its standby temperature and will thus be reactivated.

It will, of course, be understood that the ignition system of thisinvention could be provided with a manually operated switch in place ofthe automatic switch 11, a manually operated switch can be used wheneverreactivation of the igniter filament is required.

From the above description, it will be seen that the invent 1 provides asimple means and a method of maintaining an igniter rent at a standbytemperature below that which would cause objectionable deterioration ofthe filament over a long period of time, and enables reactivation of thefilament when necessary, turning any prolonged standby period.

The foregoing disclosure is to be regarded as descriptive andillustrative only, and not as restrictive or limita tive of theinvention of which obviously an embodiment may be constructed includingmodifications without departing from the general scope herein indicatedand denoted in the appended claims.

What we claim is:

1. In the operation of a catalytic iguiter coil in a gas burner, themethod including electrically heating said coil to an elevatedtemperature below that temperature at which the gas to be burned willignite, supplying electrical energy to said coil at a constant level soas to maintain said coil at the elevated temperature and obtain standbyoperation, and temporarily applying heat to said coil to increase saidelevated temperature at spaced intervals to a value sufficient tostimulate the activity of said coil while maintaining the atmospheresurrounding said coil free from any ignitable gases.

2. In the operation of a catalytic igniter coil having a heterophaseconfiguration in use in a gas burner, the method of standby operationincluding heating said coil by the passage of electric energythere-through to an elevated temperature below that temperature at whichthe gas to be burned will ignite, said aforementioned temperature beingthe stand-by temperature, supplying electrical energy to said coil at aconstant level to maintain said coil at the stand-by temperature, andtemporarily and periodically increasing the said electrical energy levelto raise the temperature of said filament coil to a value sufficient toreactivate said coil while maintaining the atmosphere surrounding saidcoil free from any ignitable gases.

3. In the operation of a catalytic igniter coil having a heterophaseconfiguration in use in a gas burner, the method of standby operationincluding passing electrical energy through said coil of a valuesufiicient to heat said coil to a. standby temperature below theignition temperature of said gas, supplying electrical energy to saidcoil at the aforementioned value to maintain said coil at the stand-bytemperature, and temporarily and at spaced intervals discontinuing thepassage of electrical energy through said coil at said first value andsimul taneously passing another higher value of electrical energythrough said coil while maintaining the atmosphere surrounding said coilfree from any ignitable gases, said second higher value being of anamount sutlicient to intermittently reactivate said filament during itsstandby operation.

4. The method of claim 2 wherein the said electric energy level passedthrough said coil is of a value sufficient to maintain the coiltemperature in the range of about 600 C. to about 800 C. and the step ofincreas ing the said electrical energy level consists in increasing theenergy level by an amount suificient to raise the filament temperatureabove 800 C.

5. The method of claim 4 wherein the voltage of the said energy level isincreased by about one and one-half times its initial value.

6. The method of claim 3 wherein said first value of electrical energyis of a value sutficicnt to attain a coil temperature in the range ofabout 600 C. to about 800 C. and the second value of electrical energyis of a value sutficient to raise the coil temperature above 809 C.

7. The method of claim 6 wherein the voltage of said second energy levelis about one and one half times the voltage of said first energy level.

8. In a gas burner having a flash-back ignition means, a catalyticigniter filament having a heterophase configuration, an electricalcircuit including a source of current and said filament, a firstbranched closed path and a second branched closed path in said circuithaving said filament as a common element therein, said first branchedclosed path being adapted to carry a lesser voltage than said secondbranched closed path, and means for normal- 1y keeping said second pathopen and for temporarily closing said second path at spaced intervalsfor supplying a surge of voltage through said filament.

9. In a gas burner having a flash back ignition means, a catalyticigniter filament having a heterophase configuration, an electricalcircuit including a source of current, a transformer having a secondarycoil and said filament, a first branched closed path and a secondbranched closed path in said circuit including as common elements aportion of s rid secondary coil and said filament, said first branchedpath being adapted to carry a lesser voltage than said second branchedpath, and switch means in said circuit biased to normally keep saidsecond branched path open and for periodically and temporarily closingsaid second path to instantaneously increase the energy that passesthrough said filament.

10. The flashback system adapted for stand-by operation of claim 9wherein one end of said secondary coil is connected to one end of saidfilament, a switch means including at least two spaced apart contacteleinents and a contact lever, said lever being normally closed againstone of said contact elements, the other end of said filament beingelectrically connected to said contact lever, said one contact elementbeing connected to said secondary coil between the ends thereof tocomplete said first branched path which is adapted to provide acontinuous supply of electric energy to said filament for heating it toan elevated temperature below that temperature at which the gas to beburned will ignite, the other of said switch contact elements beingconnected to the other end of said secondary coil to complete saidsecond branched path, said switch contact lever being adapted to beperiodically and temporarily closed to said other contact elementwhereby the passage of electrical energy through said filament isenergized with an increased voltage and the activity of said filament isstimuiated.

11. The flash-back system of claim 10 wherein said switch means includesan automatic time switching mechanism which is adapted to periodicallyand temporarily move said contact lever from said one contact element tosaid other contact element.

References Cited in the file of this patent UNITED STATES PATENTS1,118,943 Lyon Dec. 1, 1914 2,192,631 Beam Mar. 5, 1940 2,360,608Kauffman Oct. 17, 1944 2,487,752 Cohn Nov. 8, 1949 2,487,753 Cohn Nov.8, 1949 2,487,754 Cohn Nov. 8, 1949 2,530,827 Lakota et a1. Nov. 21,1950

